Previous linear motion carriage assemblies have guide rails that are unique aluminum extrusions or unique ground steel profiles that rely on features in the extrusion or rails to secure linear travel. These features are either V-grooves in the rectangular or square cross-section aluminum extrusions, or salient opposing triangular sections in unique aluminum extrusions, or groves in ground steel rails.
Linear motion assemblies built with rails having V-grooves or proud features rely on bearing wheels that have multiple angled contact surfaces to constrain degrees of freedom to allow for strict linear motion along one axis.
FIG. 1 shows prior art, with a linear motion apparatus 10 using an aluminum extrusion 20 having a V-slot profile 19, with mating radial bearing wheels 12 that contain a similar V-profile for their contact surfaces 13. The radial bearing wheels 12 include two radial cartridge bearings 15 with a spacer 16 in between the bearings 15, and an outer wheel plastic material 14. The exterior races of the bearings 15 are secured in the outer wheel material 14 by a slight compression fit. The radial bearing wheels 12 are secured to a frame 11 each by a threaded bolt fastener 21 and threaded nut fastener 22, with either a tubular spacer 17 or an eccentric nut spacer 18 ensuring the frame 11 doesn't contact the extrusion 20. Preload of the radial bearing wheel 12 preload is set by adjusting the eccentric nut spacer 18, then securing the fasteners 21 & 22.